void main() {
  // 1. num(小数，整数)
  num age = 10;
  age = 25;
  num weight = 120.78;
  print(age);
  print(weight);

  // 2. int（整数）
  int height = 188;
  // height = 172.2;
  height = 180;
  print(height);

  // 3. double(小数，整数)
  double price = 18.5;
  price = 10;
  print(price);
}
